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Full text of "Handbook Of Chemical Engineering - I"

POWER GENERATION AND TRANSMISSION                   63
the cost of producers alone. In normal times, blast-furnace gas installations (requiring only engines, buildings and gas cleaning equipment) can be set up for $100 per kilowatt.
GAS ENGINES
Fuels.  Engines using liquid fuels are considered below (page 66). Some analyses of typical gas fuels are given in the table on p. 62.
The figures in the last column of the table are no index to the value of the gas for power purposes. They do not determine engine efficiency or engine size.
Types of Engine.  Gas engines may be vertical or horizontal, the former being mainly in small sizes. They may be single or double acting: the former generate power only about half as fast, but the pistons and rods require no water cooling. Trunk pistons make for simplicity, but can be used on small engines only. Important engines are multi-cylinder, both tandem and twin arrangements being used. The latter gives smoother running and decreases overall length: it costs more.
Engines are two-cycle or four-cycle according as the sequence of operations is completed in two or four single strokes. Two-cycle engines may be of much simpler construction: they are sometimes practically valveless. They give about 70 per cent more power for their size than four-cycle types. They consume considerably more fuel per horsepower-hour. With a given number and structural arrangement of cylinders, they run more smoothly.
Capacities.  If n = number of cylinders, S = piston speed, feet per minute, a = piston area, square inches, pm = mean effective pressure, pounds per square inch, the indicated horsepower of a four-cycle single-acting engine is
-1 ~ 132000'
The two-cycle engine gives ideally twice this power. For double-acting engines,multiply these figures by 2. If EM = mechanical efficiency, the brake horse-power is H& = EM^I- Values of EM are given by Lucke as follows1
MECHANICAL EFFICIENCIES
(Lucke, " Thermodynamics")
MECH. EFFICIENCY TYPE OF ENGINE                                                         4-CYCLK          2-CYOLE
Small or medium single-cylinder, stationary, single-acting. ...      0.87           0.70
Small or medium 2-cylinder, stationary, single-acting ........      0.84      ..........
Small or medium 3-cylinder, stationary, single-acting ........      0.82      ..........
Small or medium 4-cylinder, stationary, single-acting ........      0.80      ..........
Large single-cylinder, stationary, single-acting ..............      0 . 90           0 . 70
Large 2-cylinder, stationary, single-acting ..................      0.86            to
Large 4-cylinder, stationary, single-acting ..................      0 . 84           0 . 80
Large single-cylinder, stationary, double-acting ..............      0.83           0.75
Tandem 2-cylinder, stationary, double-acting ...............      0,81           0 . 73
Tandem twin 4-cylinder, stationary, double-acting ... .......      0 . 77           0 . 69